Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$110.25	4.253%	$114.9389	$114.94	$114.95	$114.90
Purchase #2	$26.52	8.545%	$28.7861	$28.79	$28.80	$28.80
Purchase #3	$94.61	5.580%	$99.8892	$99.89	$99.90	$99.90
Purchase #4	$58.85	4.555%	$61.5306	$61.53	$61.55	$61.50
Purchase #5	$66.35	9.432%	$72.6081	$72.61	$72.60	$72.60
Purchase #6	$230.71	7.730%	$248.5439	$248.54	$248.55	$248.50
Purchase #7	$117.56	12.290%	$132.0081	$132.01	$132.00	$132.00
7 purchase totals =	$704.85		$758.3049	$758.31	$758.35	$758.20